WHAT DIGITAL FLY-BY-WIRE CHANGED
The A320 was not the first aircraft ever to transmit flight-control commands electrically: military aircraft and Concorde preceded it. Its historical distinction concerns fully digital fly-by-wire in this generation of commercial airliner. Computers process pilot or autopilot commands before actuators move the surfaces. Airbus itself places the technology in that wider development history, which is more precise than saying the A320 invented fly-by-wire. [20, Definition and historical development]
The operational consequence is the control law. In normal law, the sidestick command and aircraft response are mediated by that law and its protections. After relevant failures, both the response and available protections can change. The same physical stick therefore does not imply the same underlying relationship in every condition. The flight-control chapters examine those states directly, without treating fly-by-wire as a promise of protection against every possible outcome. [4, Flight controls; normal, alternate and direct-law overview]
A useful simulator habit follows: identify the active law and guidance mode before interpreting an unexpected response. A manual input, flight-director command and autopilot action are different things to observe. Understanding their relationship turns the historical idea into useful cockpit knowledge. [21, Flight controls and use of automation; applicable standard]